The sum of oxidation states of all atoms in $Cr_{2}O_{7}^{2-}$ ion is

Arrange the following molecules in the increasing order of the oxidation number of $S$: $SO_3^{2-}$,$S_2O_4^{2-}$,and $S_2O_6^{2-}$.

What is the oxidation state of oxygen in $OF_2$?

The oxidation number of $Cr$ in $K_3CrO_8$ is $+5$. How many peroxy linkages are present in this molecule?

The oxidation number and the electronic configuration of sulphur in $H_2SO_4$ is

Assign the oxidation number to the underlined element in each of the following species:
$1$. $NaH_{2}\underline{P}O_{4}$
$2$. $NaH\underline{S}O_{4}$
$3$. $H_{4}\underline{P_{2}}O_{7}$